Rapid cooling technology could aid surgery patients, heart attack victims

ARGONNE, Ill. (Oct. 28, 2005) — A promising new approach to saving stroke and cardiac arrest victims is also being investigated as a technique to improve laparoscopic surgery. Researchers at Argonne National Laboratory and the University of Chicago have developed a specially engineered ice slurry that cools organs, allowing doctors more time to treat patients.

The core idea is to rapidly cool the blood of targeted organs with a highly fluid mixture of small, smooth ice particles suspended in saline solution. For sudden stroke or heart attack, rapid blood cooling could delay the death of heart and brain cells, giving doctors and paramedics more time to revive victims.

Ice slurry technology could also give surgeons more time to perform minimally invasive laparoscopic surgery, which frequently requires temporarily stopping blood flow to small organs, such as kidneys or the liver. Cooling these organs before stopping their blood supply would give surgeons more time to operate before organ cells began to die from lack of oxygen.

"In the United States alone," said Roger Poeppel, director of Argonne's Energy Technology Division, "sudden cardiac arrests strike about 1,000 people a day, and the survival rate is at best 2 to 4 percent. If we can improve the survival rate by just 1 percent, we will save the lives of 10 people every day."

People who suffer cardiac arrests outside of the hospital have a lower recovery rate. Ten to 12 minutes after an arrest, brain cells start dying rapidly because of lack of blood flow to the brain.

In 1999, Ken Kasza, a senior mechanical engineer who leads the research at Argonne, and Poeppel worked with Lance Becker and Terry Vanden Hoek, both medical doctors from the University of Chicago Hospitals, to start the Emergency Resuscitation Center. Headed by Becker and Vanden Hoek, the center is dedicated to studying health problems like cardiac arrest.

When the team began their research they knew that when cells are cooled, their metabolism and chemical processes slow dramatically. For example, a skater who falls into an icy pond can often be resuscitated even after being submerged for many minutes.

Because external cooling works too slowly, the team proposed to inject ice slurry into the body to induce faster, internal cooling. Because of its high cooling capacity, associated with ice melting, a small amount of slurry could rapidly and effectively cool critical organs.

The result of years of research and development, the ice slurry is specially engineered to have rounded particles and special flow characteristics that allow it to be pumped easily through small tubes.

In the procedure, slurry would be delivered into the lungs or other organs, such as the stomach, which are used as in-body heat exchangers to cool the surrounding blood. For cardiac arrest, medics would perform chest compressions to circulate the cooled blood, allowing it to reach the brain and preserve brain cells. The ice slurry melts in the body, where it acts much like drip bag saline solution.

Data collected by the Argonne-University of Chicago team show that the ice slurry cools the brain by 2 to 5 degrees Celsius in a few minutes, which is much faster than any other method currently available. For example, external cooling by chilling blankets can take 3 to 5 hours, which is much too slow in an emergency such as cardiac arrest. The ice slurry appears to keep the brain cool for an hour, which would give medics and doctors more time to revive normal blood flow and brain activity. This extra time could reduce the brain damage to little or none.

For heart attacks, the ice slurry procedure would be secondary to defibrillation. In a real scenario, medics at a scene would start with the defibrillator, but if the heart did not respond, they would begin immediate cool down.

The team is currently working on further expanding the ice slurry's medical applications beyond cooling the heart and brain. Working with Dr. Arieh Shalhav, a University of Chicago surgeon, they are testing the effectiveness of ice slurries in cooling kidneys during laparoscopic surgery. Research has shown that the ice slurry can be readily delivered by a small tube through existing laparoscopic surgery penetration ports using endoscope viewing to guide coating the external surface of an organ, cooling it 15 degrees C or more in 10 minutes.

Development of this technology is funded by the National Institutes of Health.

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